KR102012838B1 - Method of protecting the end of a multi-tendon cable - Google Patents

Abstract

The method of the invention protects an end of a cable which is made of a plurality of parallel tendons 10 and fixed using an anchor block 15 having a front, a back and channels 16 extending between the front and back. It is to. Each tendon of the cable is retained in each channel of the anchor block with a blocking member 19. The method includes performing a first injection step of the protective material 100 on at least some of the channels of the anchor block. The chamber 30 is formed on at least one side of the anchor block 15 to include portions of the plurality of tendons. Thereafter, a second injection step of the protective material 200 is performed in the chamber 30.

Description

METHOD OF PROTECTING THE END OF A MULTI-TENDON CABLE}

The present invention relates to structural cables used in construction work. This applies in particular for tension cables or prestressing cables.

Such structural cables are frequently made of a plurality of parallel tendons. Their ends are secured with blocks, for example, where channels are formed for individually receiving and blocking tendons by split conical jaws.

The tendons of the cables are made of metal in the form of strands, for example. In the main part of the cables, they are often enclosed in separate sheaths of plastic material that isolate from the environment and thus protect from caustic. In order to hold the tendon firmly in the anchor block, the plastic cover is removed from the anchoring area. It is then necessary to provide special anti-corrosion protection to the anchoring areas. In general, the space containing the exposed portion of the tendon is filled with a protective material which is injected under pressure in the anchoring zone.

The injection step should be carried out carefully to fill any voids remaining in the space, since these voids can be the starting point of corrosion for tendon metals, especially when water is infiltrated.

Considering the properties of adhesion, corrosion protection and fatigue behavior, it is an example of interest as a protective material in which wax is injected into the anchoring zone. The wax is solid at room temperature and becomes liquid when heated. Thus it can form a reversible filling and is useful for anchorage testing.

Other injectable protective materials may in particular be used thick materials such as grease or hardening materials such as resins or polymers.

For a given construction job, the protective material is selected taking into account the necessary functions for anchorage hypothesis or maintenance.

The space filled with protective material includes a chamber located in front of the anchorage and closed by a cover. Ends of the tendon cable protruding from the anchorage are located in the chamber.

In certain anchorage designs (see eg WO 01 / 20098A1), there is a second chamber behind the anchor block, in which the individual cover end of the tendons is located. The rear surface of the second chamber is closed by a sealing device such as a box type filled with the cover part of the tendons extending through. Filling the second chamber with the protective material may be performed separately or simultaneously with filling the first chamber located in front of the anchorage. When filling at the same time, one or more communication channels in addition to the channels containing tendons are generally provided through the anchor block to allow the injection material to flow.

In another kind of anchorage design (see eg EP 0 EP896 108 A2 or EP 1 227 200 A1), the back side of the anchor block does not have second chambers collectively containing tendons. Individual cover ends of the tendons are located in the extension of these channels provided in the channel of the anchor block or at the rear of the anchor block.

Injection is performed after the tendons are installed and tensioned. Typically, the filler material is injected into the inlet located at the bottom of the anchorage until it flows out of the vent located at the high portion of the anchorage. This minimizes the risk of leaving gaps in the filled space.

However, it does not completely eliminate the risk. When the level of the filling material rises and touches the anchor block, it forms a flow path in which other channels compete. The head loss in these channels is not uniform because the contents of the channels may vary from channel to channel. For example, if the block has one or more communication channels in addition to the channels containing tendons, the fluid material tends to flow through the communication channels, leaving other channels empty, thus exposing metal tendons. There may be debris in the channel at the beginning of the injection, which creates the risk of the headloss being changed and incompletely filled through the channel. If there are no communication channels at all and / or there is a chamber only in front of the anchorage, it is very difficult to ensure that the channels including tendons are completely filled.

Accordingly, there is a need for an improved method of filling the interior space of an anchorage system to protect tendons and other metal components of anchorage from corrosion.

A method of protecting the end of a cable made of a plurality of parallel tendons is proposed. The cable is secured using an anchor block having a front side, a rear side and channels extending between the front side and the rear side, the number of channels being at least equal to the number of tendons of the cable. Each tendon of the cable is retained in each channel of the anchor block with a blocking member. The method is:

Performing a first injection of the protective material in at least some of the channels of the anchor block;

An end of the plurality of tendons, forming a chamber at least in front of the anchor block; And

And performing a second injection step of the protective material in the chamber.

The first injection step can ensure that the channels are properly filled. In particular, the channels can be filled separately by injecting a controlled amount of protective material. In general, each channel of the anchor block containing tendons receives the protective material in the first injection step.

The protective material injected into the channel of the anchor block in the first step may be wax or grease.

In one embodiment, the first injection step is for each channel:

Sealingly attaching the bell-shaped cover to the inlet of the channel;

Injecting the protective material inside the bell-shaped cover to push the protective material into the channel; And

Removing the bell-shaped cover.

For a channel containing tendons of the cable, the bell-shaped cover may have a passage for the tendons. It can then attach a bell-shaped cover to the tendon when the protective material is injected to withstand the injection pressure.

The proposed method is also advantageous in that the protective material injected into the chamber in the second step can be chosen differently from the protective material injected into the channel of the anchor block in the first step. The choice of protective material is made as a function of certain functions for each part of the anchorage in order to optimize the properties of the anchorage.

The method may be applied to an anchorage having two parts each in front and rear of the anchor block connected together by at least one communication channel in which the chamber extends through the anchor block. Preferably, the communication channel is not filled with the protective material in the first injection step. In most cases, no cable tendons will be placed on these communication channels. The second injection step may have a common step of injecting a protective material into one of the parts of the chamber and from said one of the parts of the chamber to another part of the chamber via at least one communication channel.

This may also apply to anchorages where the chamber is only at the front of the anchor block. The chamber comprises ends of the plurality of tendons of the cable and contains a protective material, such as wax or grease, in the second injection step.

This may further apply to an anchorage having two chambers, a first chamber comprising tensioned portions of tendons formed on the back side of the anchor block and a second chamber comprising ends of tendons formed on the front side of the anchor block. In this embodiment, the second injection step includes injecting the protective material into the second chamber separately from the step of injecting the protective material into the first chamber. The protective material, for example polymer or resin, may be chosen differently from the protective material, such as wax or grease, which is injected into the second chamber.

Other features and advantages of the methods and apparatus herein will become apparent from the non-limiting examples below with reference to the accompanying drawings.

Included in the context of the present invention.

1 is a schematic diagram of an exemplary anchoring device for a rescue cable in a first injection step.
2-4 are schematic views of the anchoring device of FIG. 1 in different steps of the method according to an embodiment of the invention.
5 is a schematic view of another embodiment of an anchoring device.

The structural cable shown in FIG. 1 is made of a plurality of tendons 10 each composed of metal strands 11 contained in individual plastic sheaths 12. Only two tendons 10 are shown in the figure for simplicity. In general, larger numbers of tendons, such as dozens of tendons, are used. Tendons 10 extend alongside each other along a designated path of the structural cable, for example, along an inclined path of the tension cable between the deck and the pylon of the bridge, or along a path designated for the prestretching cable.

The rescue cable is fixed at both ends. The anchoring devices transfer the tensile load of the cable to the structure.

In order to firmly grip the tendons 10 in the anchoring device, the plastic sheath 12 is removed at the ends of the tendons 10 and thus exposes the metal of the strand 11. At each end of the cable, the exposed portions of tendons 10 extend beyond the anchor block 15 of the anchor device. The anchor block 15 has many channels 16 extending between the rear face 17 and the front face 18 (toward the successive portions of the cable where the tendons are to be tensioned). Each tendon 10 is received in one of the channels 16 having a blocking member 19.

In the illustrated embodiment, each channel 16 designed to receive tendons 10 is tapered outwardly toward the front 18 of the anchor block 15 in diameter near the back 17 of the anchor block 15. It has a cylinder portion which is slightly larger than the diameter of the strand 11 extending by the cone portion. The blocking member is in the form of a conical jab 19 disposed in the cone of the channel 16 for gripping the metal strand 11. The jaw 19 has a plurality of sectors (eg, three) held together by a ring 20 inserted into an annular groove located near the wide end of the jaw 19 having a cylindrical shaft hole for receiving the strands. Sectors).

In order to lay the cable, tendons 10 are inserted into the respective channels 16 with conical jaws 19 and the strands 11 at the portions protruding from the front face 18 of the anchor block 15. Tension is applied by holding them, using an actuator such as a hydraulic jack to pull them, and forcing the jaw 19 into the channel 16. If the actuator is inoperative, the jaw 19 shuts off the strands 11 in these channels 16. This tensioning operation can be performed for the entire cable on a strand basis, on a strand group basis or collectively.

After the cable is tensioned, some gaps remain in the channel 16, particularly around the strand 11 in the cylinder and between the jaw sectors in the cone.

A first injection step is performed to ensure that these gaps are filled with the material 100 which prevents the metal from corroding.

In one embodiment, the material in which channel 16 is filled in the first injection step is wax or grease. However, it may also be a curing material such as a polymer or a resin.

As shown in FIG. 1, a first injection step can be performed for each channel 16 using a bell shaped cover 25 over the inlet of the channel. The cover 25 is hermetically attached to the front face 18 of the anchor block 15 using a gasket 26, the opposite end having an opening that provides a passage for the strand 11. A sealing ring 27 is disposed around the strand 11 to seal the front end of the cover 25 which is fixed in position by a ring 28 fixed to the free end of the strand 11.

The protective material 100 is ejected in a fluid or soft step through the inlet 29 formed in the cover 25. Since the volume of gaps not occupied by the metal strands and jaws is known exactly, a controlled amount of protective material can be injected into each channel 16 to ensure that the channels are completely filled. An injection pump (not shown) is controlled to inject a set amount of protective material 100 into the cover 25 to completely fill the channel 16.

Attaching the bell shaped cover 25 to the strand 11 ensures that the cover 25 is maintained at the inlet of the channel 16 while the protective material is pressurized and ejected to overcome the headloss in the channel 16. . In this step, it will be appreciated that other ways may be used which may be used, for example, to retain the cover attached to the anchor block 15.

Fill material 100 injected into channel 16 is hardened to harden (if polymer or resin) or by cooling (if wax), and cover 25 is removed from the front of anchor block 15 . If the fill material 100 is a thick material such as grease, no curing time is required and the cover can be removed immediately after injection. The amount of protective material 100 may or may not remain in the portion of the strand 11 contained in the cover 25.

After the first injection step, a second injection step is performed to fill the other closed space (s) of the anchorage with the protective material. In the embodiment illustrated in FIGS. 1 to 4, two chambers are filled, one chamber 30 in the back of the anchor block 15 and one chamber 31 in the front. These two chambers 30, 31 are separately filled with protective material 200, 300.

The first chamber 30 of the anchor block back surface 17 is radially bounded by a tube 32 in which the tensioned portion of the tendon 10 is expanded. The ends of the tendon plastic cover 12 are located in the chamber 30. Opposite the anchor block 15, the chamber 30 is a chamber as described in WO 01 / 20098A1 which disconnects the chamber 30 from the outside while leaving a passageway for the sealing device 34, for example tendon 10. Is closed by a filled box fixture.

In this example, the front end of the tube 32 has a flange 33 forming a bearing surface for the anchor block 15, which flange 33 is applied to a cable-equipped structure. It will be appreciated that the anchorage may have a variety of other arrangements within the scope of the present invention.

Injection of the protective material 200 into the first chamber 30 (FIG. 2) is performed in the illustrated example through an inlet formed by the opening 35 provided in the anchor block 15 below the chamber 30. In the structure shown, the opening 35 is bent to access the side of the anchor block 15. It is straight and can access the front face 18 of the anchor block 15. A vent 36 is formed on top of the tube 32 to exhaust the air contained in the chamber 30 during the injection step. Once the injection is complete, the vent 36 is plugged with a plug 37 (FIG. 3) and the protective material 200, if necessary, hardens or solidifies before plugging the inlet opening 35 with another plug 38. It is done.

The second chamber 31 on the front face 18 of the anchor block is bounded by the case 40 shown in FIG. 4. The case 40 is mounted to the anchor block 15 by bolts or other fastening means (not shown). A sealing ring 41 is provided between the rear end of the case 40 and the front face 18 of the anchor block to prevent the protective material from leaking upon injection. The case 40 is dimensioned to include the exposed ends of all tendons 10 of the cable. The lower part of the case has an opening 42 for injecting the protective material 300 and the upper part of the case has a vent 43 for discharging air when the protective material 300 is injected.

The protective material 300 injected into the second chamber 31 fills all remaining gaps. When it flows out through the vent 43, the injection stops and the plug 45 is placed in the vent 43. The injected protective material 300, if necessary, is cured or solidified before plugging the inlet opening 42 with another plug.

The protective material injected to fill (i) the channel 16, (ii) the chamber 30 at the rear of the anchor block 15 and (iii) the chamber 31 at the front of the anchor block 15 may be filled. It can be selected irrespective of each space, thus allowing optimization of the anchorage by selecting a material that meets the desired properties.

The chamber 31, located in front of the anchor block 15, can be opened to check for proper operation by removing the case 40 during the life of the anchorage. For this reason, it is generally desirable to use a protective material 300 for the chamber 31 that can be easily removed. Wax is an advantageous material for this purpose because it can be melted or at least softened and pumped by heating. Christ can also be used.

Gripping and anchoring of tendons 10 occur in channel 16. Flexible materials 100 having lubricating properties, such as grease or wax, may be suitable in view of good fatigue behavior that enhances ultimate strength of tendons.

The chamber 30 at the back of the anchor block 15 is potentially exposed to the ingress of water flowing along the structure or cable. Flexible, viscous and coherent material 200 is often a good choice to best prevent this penetration. A polymer or resin is advantageously injected into this part of the anchorage.

5 shows another embodiment of an anchoring device in which a second injection step, after filling of channels 16 in which tendons are blocked, is basically carried out in one step. The filled chamber is thus made of two parts 50, 51 connected together by one or more communication channels 52. The first part 50 is located on the rear face 17 of the anchor block 15 and is bounded by the box type and cylinder tube 32 filled in the sealing device 34, FIGS. 1 to 4. Functionally similar to the first chamber 30 of the embodiment shown in FIG. The second part 51 is functionally similar to the second chamber 31 of the embodiment shown in FIGS. 1 to 4, which is located on the front face 18 of the anchor block 15 and bounded by the case 40. Do. The communication channel 52 does not include tendons and extends through the anchor block 15 parallel to the channels 16 including the tendons.

After hypothesis and tensioning of tendons 10, a first injection step is performed to fill channel 16 with protective material 100 as described with reference to FIG. 1. The case 40 is then assembled to the anchor block 15 and a second injection step is performed to inject the protective material 400 into the two part chambers 50, 51.

The example of FIG. 5 is for example an anchorage at the bottom of an inclined tension cable. In this configuration, the bottom of the anchorage is at the bottom of the case in which the inlet 42 is formed. As in the previous embodiment, two vents 36 and 43 are provided, one vent 36 is on top of the rear portion 50 of the chamber and the other vent 43 is on top of the front portion 51 of the chamber. Is in. During the second injection step, the level of fluid material 400 rises. When the material reaches the vent 43, a plug 45 is placed in the vent 43 to overflow and continue the injection so that the protective material 400 is further passed through the communication channel 52 to the rear portion 50 of the chamber. To rise. When the other vent 36 is reached, the second injection step ends and the plug is placed in the vent 36. Protective material 400 may be cured or solidified, if necessary, before clogging inlet opening 42 with another plug.

In the embodiment of FIG. 5, the protective material 400 injected into the chambers 50 and 51 in the second step is preferably not necessarily necessary, but with the protective material 100 injected into the channel 16 in the first step. same. For example, wax or grease may be injected into the channel 16 and then into the two parts of the chamber 50, 51. However, it may be desirable to use other filling materials for certain job specifications.

In another embodiment, the chamber filled in the second injection step is located only in front of the anchor block 15. The plastic sheath 12 of the tendons 10 then has an end in the individual extensions of these channels either inside the channel 16 of the anchor block 15 or behind the anchor block 15.

In this case, the first injection step is performed to fill the channel 16 and / or the extensions of the channel with the protective material 100. Filling in at least a portion of the channel 16 and / or the extension of the channel without plastic cover in the strand metal is done. By separately injecting the protective material into the channel 16 and / or the extension of the channel, it is reliably ensured that the filling is independent of the variable head loss normally experienced by the injected material in these channels.

Thereafter, the previously injected protective material 100 and other protective material 300 are preferably transferred to the chamber 31 which is located only on the front face 18 of the anchor block 15 and includes the ends of the strand 11. A second injection step is performed to introduce. This can be done in the manner as described with reference to FIG. 4.

If the chamber 31 filled with the protective material is located only on the front of the anchor block 15, the wax or grease will remove relatively good fatigue (for the channel 16) and relatively (for the chamber 31). It is often an easy choice for the protective material in both the channel 16 and the chamber 31. However, other options may also be suitable or desirable. For example, waterproofing may be a concern at the back of the channel, such as an anchorage design. For this reason, an adhesive fill material such as polymer or resin can be used in the channel 16, while wax or grease is injected into the chamber 31.

The above-described method of protecting the exposed ends of the tendons of the structural cable using two or more injection steps in other parts of the anchoring device can be applied to the installation of a new cable. This may also apply to maintenance or repair of existing cables. In this case, the protective filling material previously located in the other parts of the anchoring device is filed (eg, March 28, 2011) before injecting one or more new protective material (s) in two or more steps as described above. Using the method as described in French Patent Application No. 11 52557).

Although the foregoing description of exemplary embodiments of the invention has been given above, various alternatives, modifications, and equivalents will be apparent to those skilled in the art.

In particular, the above-described choice for the protective materials to which other anchoring portions are filled is a design optimization problem and may vary depending on the desired functions for a particular anchorage design with a particular geometric configuration or arrangement.

The hypothesis described above to fill one or more chambers on one or both sides of the first channel 16 including tendons and then the anchor block 15 using several injection steps even uses the same protective material for all parts of the anchorage. It will also be evident to provide the advantage of ensuring adequate filling and protection of the metal tendons even if so.

Claims (15)

A cable made of a plurality of parallel tendons 10 and secured using an anchor block 15 having a front face 18, a back face 17 and channels 16, 52 extending between the front face and the back face. As an end protection method of
Each of the tendons of the cable includes a metal strand 11 and a separate plastic sheath 12 containing the metal strands, wherein the individual plastic sheaths 12 of each of the tendons of the cable are formed of the anchor block. Stopped at the rear side, the metal strand 11 of each of the tendons is retained in each channel of the anchor block with a blocking member 19,
Performing a first injection step of the protective material 100 on at least some of the channels 16 of the anchor block;
Forming a chamber (31; 50-51) at least in front of the anchor block, wherein the ends of the metal strands (11) of the tendons located in front of the blocking member (19) are received in the chamber ; And
Performing a second injection step of the protective material (300; 400) in the chamber, whereby the protection material injected in the second injection step is brought into contact with the ends of the metal strand. . The method of claim 1,
Each channel (16) of the anchor block (15) to which the metal strands (11) are fixed is the end protection method of the cable which receives the protective material (100) in the first injection step. The method of claim 1,
The first injection step is for each channel 16:
Sealingly attaching the bell-shaped cover 25 to the inlet of the channel;
Injecting the protective material 100 into the bell-shaped cover to push the protective material into the channel; And
-Removing the bell-shaped cover. The method of claim 3, wherein
The bell shaped cover 25 has a passageway for the metal strand 11 of the tendon 10 of the cable extending through the channel 16, which bell shaped covers when the protective material 100 is injected into the bell shaped cover. A method of protecting the ends of cables attached to metal strands. The method according to any one of claims 1 to 4,
The protective material (100) injected into the channel (16) of the anchor block (15) in the first injection step is wax or grease. The method according to any one of claims 1 to 4,
The protective material 300; 400 injected into the chambers 31; 50-51 in the second step is the end of the cable different from the protective material 100 injected into the channel 16 of the anchor block 15 in the first step. How to protect. The method according to any one of claims 1 to 4,
The chamber has at least two parts 50, 51 on the front and back of the anchor block, respectively connected together by at least one communication channel extending through the anchor block 15, the protective material communicating in the first injection step. The second injection step, which is not injected into the channel, has a common step of injecting the protective material 400 into one of the parts of the chamber and from one of the parts of the chamber to another part of the chamber via at least one communication channel. How to protect the ends of the cable. The method of claim 7, wherein
A method of protecting an end of a cable in which no tendons of the cable are placed in the communication channel (52). The method according to any one of claims 1 to 4,
A first chamber 30 including tensioned portions of tendons 10 is formed on the back side 17 of the anchor block 15, and the individual plastic sheathing of each tendon of the cable is in the first chamber 30. And a second chamber 31 comprising ends of the metal strand of the tendon is formed on the front surface 18 of the anchor block, and the protective material 200, 300 is injected into the first chamber and a separate second chamber. How to protect the end of. The method of claim 9,
The protective material (200) injected into the first chamber (30) is different from the protective material (300) injected into the second chamber (31). The method of claim 10,
Protective material (200) injected into the first chamber (30) is a method of protecting the end of the cable is a polymer or resin. The method of claim 10,
The protective material (300) injected into the second chamber (31) is wax or grease. The method according to any one of claims 1 to 4,
A chamber is formed only in front of the anchor block 15, the chamber comprising an end of the metal strand 11 of tendons 10 of a cable and receiving the protective material in the second injection step. . The method of claim 13,
Protective material (300) injected into the chamber in the second injection step is a method of protecting the end of the cable is wax or grease. The method of claim 13,
The protective material (100) injected into the channel (16) of the anchor block (15) in the first injection step is a polymer or resin end protection method.

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